Different impacts of respiratory symptoms and comorbidities on COPD-specific health-related quality of life by COPD severity

Figures & data

Figure 1 Flowchart of the study population.

Abbreviations: COPD, chronic obstructive pulmonary disease; KOCOSS, Korean COPD Subgroup Study; SGRQ-C, St George’s Respiratory Questionnaire for COPD.

Figure 2 Correlation between SGRQ-C total score and post-BD FEV₁ (% predicted) in patients with mild-to-moderate COPD.

Abbreviations: BD, bronchodilator; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in one second; SGRQ-C, St George’s Respiratory Questionnaire for COPD.

Figure 3 Correlation between SGRQ-C total score and post- BD FEV₁ (% predicted) in patients with severe-to-very severe COPD.

Abbreviations: BD, bronchodilator; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in one second; SGRQ-C, St George’s Respiratory Questionnaire for COPD.

Table 1 Clinical characteristics of mild-to-moderate COPD patients according to SGRQ-C score

	Total (n=902, 100%)	SGRQ-C ≥25 (n=534, 59.2%)	SGRQ-C <25 (n=368, 40.8%)	p-value
Age, years	69.0±7.6	69.9±7.6	67.9±7.5	0.001
Sex, male	801 (88.8)	467 (87.5)	334 (90.8)	0.122
Body mass index, kg/m^2	23.4±3.3	23.4±3.4	23.4±3.1	0.803
Body mass index ≤21 kg/m^2	210 (23.3)	125 (23.4)	85 (23.1)	0.914
Smoking status
Current smoker	256 (28.4)	148 (27.7)	108 (29.3)	0.325
Ex-smoker	538 (59.6)	328 (61.4)	210 (57.1)
Never smoker	108 (12.0)	58 (10.9)	50 (13.6)
Education
≤ High school education	781 (86.6)	487 (91.2)	294 (79.9)	<0.001
≥ College education	121 (13.4)	47 (8.8)	74 (20.1)
Area of residence
Large city	484 (53.7)	286 (53.6)	198 (53.8)	0.186
Small- and medium-sized cities	253 (28.0)	143 (26.8)	110 (29.9)
Rural area	160 (17.7)	100 (18.7)	60 (16.3)
Other	5 (0.6)	5 (0.9)	0 (0)
Respiratory symptoms
Cougha	203 (22.5)	153 (28.7)	50 (13.6)	<0.001
Sputuma	279 (30.9)	192 (36.0)	87 (23.6)	<0.001
Dyspnea (≥ mMRC II)a	301 (33.4)	245 (45.9)	56 (15.2)	<0.001
Comorbiditiesa
Number of comorbiditiesb	2 (1–3)	2 (1–3)	2 (1–3)	0.002
Myocardial infarction	46 (5.1)	30 (5.6)	16 (4.3)	0.114
Congestive heart failure	31 (3.4)	24 (4.5)	7 (1.9)	0.030
Peripheral vascular disease	23 (2.5)	17 (3.2)	6 (1.6)	0.113
Diabetes mellitus	152 (16.9)	99 (18.5)	53 (14.4)	0.242
Hypertension	376 (41.7)	236 (44.2)	140 (38.0)	0.058
Osteoporosis	43 (4.8)	31 (5.8)	12 (3.3)	0.020
Gastroesophageal reflux disease	90 (10.0)	60 (11.2)	30 (8.2)	0.017
Hyperlipidemia	103 (11.4)	71 (13.3)	32 (8.7)	0.008
Thyroid disease	22 (2.4)	14 (2.6)	8 (2.2)	0.011
Bronchiectasis	54 (6.0)	34 (6.4)	20 (5.4)	0.130
Chronic bronchitis	70 (7.8)	42 (7.9)	28 (7.6)	0.142
Previous history or current status of TB	211 (23.4)	135 (25.3)	76 (20.7)	0.186
Previous history of pneumonia	134 (14.9)	92 (17.2)	42 (11.4)	0.008
Asthma	388 (43.0)	219 (41.0)	169 (45.9)	0.064
Allergic rhinitis	96 (10.6)	67 (12.5)	29 (7.9)	0.001
Beck’s depression inventory score ≥16c	34/198 (17.2)	22/91 (24.2)	12/107 (11.2)	0.016
6-min walk distance, m	377.1±112.7 (n=720)	358.9±107.7 (n=424)	403.1±114.8 (n=296)	<0.001

Notes: Data are shown as mean (± SD) or number (%).

a The numbers of missing/unknown data are as follows: cough (n=10), sputum (n=12), myocardial infarction (n=38), congestive heart failure (n=38), peripheral vascular disease (n=43), diabetes mellitus (n=8), hypertension (n=7), osteoporosis (n=31), gastroesophageal reflux disease (n=42), hyperlipidemia (n=46), thyroid disease (n=39), bronchiectasis (n=97), chronic bronchitis (n=106), previous history or current status of TB (n=29), previous history of pneumonia (n=51), asthma (n=43), and allergic rhinitis (n=39).

b Depression was not included in the number of comorbidities.

c Evaluated in 198 patients.

Abbreviations: COPD, chronic obstructive pulmonary disease; mMRC, modified Medical Research Council; SGRQ-C, St George’s Respiratory Questionnaire for COPD; SD, standard deviation; TB, tuberculosis.

Table 2 Clinical characteristics of severe-to-very severe COPD patients according to SGRQ-C score

	Total (n=362, 100%)	SGRQ-C ≥25 (n=291, 80.4%)	SGRQ-C <25 (n=71, 19.6%)	p-value
Age, years	68.0±7.9	68.4±8.2	66.7±6.6	0.055
Sex, male	347 (95.9)	278 (95.5)	69 (97.2)	0.745
Body mass index, kg/m^2	21.5±3.3	21.4±3.3	21.8±2.9	0.282
Body mass index ≤21 kg/m^2	174 (48.1)	148 (50.9)	26 (36.6)	0.031
Smoking status
Current smoker	82 (22.7)	64 (22.0)	18 (25.3)	0.051
Ex-smoker	256 (70.7)	212 (72.9)	44 (62.0)
Never smoker	24 (6.6)	15 (5.1)	9 (12.7)
Education
≤ High school education	321 (88.7)	258 (88.7)	63 (88.7)	0.986
≥ College education	41 (11.3)	33 (11.3)	8 (11.3)
Area of residence
Large city	162 (44.8)	128 (44.0)	34 (47.9)	0.513
Small- and medium-sized cities	140 (38.7)	112 (38.5)	28 (39.4)
Rural area	57 (15.7)	49 (16.8)	8 (11.3)
Other	3 (0.8)	2 (0.7)	1 (1.4)
Respiratory symptoms
Cougha	98 (27.1)	88 (30.2)	10 (14.1)	0.014
Sputuma	120 (33.1)	110 (37.8)	10 (14.1)	<0.001
Dyspnea (≥ mMRC II)a	220 (60.8)	201 (69.1)	19 (26.8)	<0.001
Comorbiditiesa
Number of comorbiditiesb	2 (1–3)	2 (1–3)	2 (1–3)	0.298
Myocardial infarction	20 (5.5)	15 (5.2)	5 (7.0)	0.304
Congestive heart failure	17 (4.7)	13 (4.5)	4 (5.6)	0.234
Peripheral vascular disease	9 (2.5)	8 (2.7)	1 (1.4)	0.205
Diabetes mellitus	66 (18.2)	53 (18.2)	13 (18.3)	1.000
Hypertension	127 (35.1)	96 (33.0)	31 (43.7)	0.178
Osteoporosis	16 (4.4)	16 (5.5)	0 (0)	0.023
Gastroesophageal reflux disease	30 (8.3)	25 (8.6)	5 (7.0)	0.362
Hyperlipidemia	24 (6.6)	19 (6.5)	5 (7.0)	0.544
Thyroid disease	3 (0.8)	2 (0.7)	1 (1.4)	0.265
Bronchiectasis	32 (8.8)	25 (8.6)	7 (9.9)	0.167
Chronic bronchitis	27 (7.5)	26 (8.9)	1 (1.4)	0.073
Previous history or current status of TB	107 (29.6)	90 (30.9)	17 (23.9)	0.057
Previous history of pneumonia	64 (17.7)	58 (19.9)	6 (8.5)	0.003
Asthma	172 (47.5)	137 (47.1)	35 (49.3)	0.077
Allergic rhinitis	38 (10.5)	30 (10.3)	8 (11.3)	0.171
Beck’s depression inventory score ≥16c	21/124 (16.9)	17/87 (19.5)	4/37 (10.8)	0.236
6-min walk distance, m	336.3±119.0 (n=264)	320.9±119.3 (n=211)	397.1±97.3 (n=53)	<0.001

Notes: Data are shown as mean (± standard deviation) or number (%).

a The numbers of missing/unknown data are as follows: cough (n=3), sputum (n=6), myocardial infarction (n=10), congestive heart failure (n=11), peripheral vascular disease (n=11), diabetes mellitus (n=2), hypertension (n=5), osteoporosis (n=10), gastroesophageal reflux disease (n=9), hyperlipidemia (n=8), thyroid disease (n=8), bronchiectasis (n=22), chronic bronchitis (n=26), previous history or current status of TB (n=14), previous history of pneumonia (n=16), asthma (n=18), and allergic rhinitis (n=14).

b Depression was not included in the number of comorbidities.

c Evaluated in 124 patients.

Abbreviations: COPD, chronic obstructive pulmonary disease; mMRC, modified Medical Research Council; SGRQ-C, St George’s Respiratory Questionnaire for COPD; TB, tuberculosis.

Table 3 Multivariate logistic regression analysis of the factors associated with high SGRQ-C score (SGRQ-C score ≥25) in mild-to-moderate COPD patients

	Adjusted OR (95% CI)	p-value
Model 1
Age, years	1.02 (1.001–1.04)	0.040
Sex, male	0.57 (0.31–1.06)	0.076
Body mass index ≤21 kg/m^2	0.99 (0.70–1.42)	0.973
Smoking status
Never smoker	Reference	–
Ex-smoker	2.01 (1.01–3.70)	0.024
Current smoker	2.01 (1.06–3.81)	0.033
Education ≤ high school education	2.51 (1.61–3.89)	<0.001
Cougha	2.21 (1.43–3.42)	<0.001
Sputuma	1.16 (0.80–1.68)	0.447
Dyspnea (≥ mMRC II)a	4.06 (2.87–5.73)	<0.001
Number of comorbiditiesb	1.19 (1.07–1.32)	0.001
Model 2
Comorbiditya
Myocardial infarction	1.35 (0.68–2.69)	0.388
Congestive heart failure	2.81 (1.14–6.95)	0.025
Peripheral vascular disease	1.85 (0.69–5.02)	0.224
Diabetes mellitus	1.46 (0.98–2.17)	0.061
Hypertension	1.33 (0.98–1.79)	0.066
Osteoporosis	1.22 (0.57–2.59)	0.610
Gastroesophageal reflux disease	1.46 (0.88–2.44)	0.148
Hyperlipidemia	1.77 (1.10–2.87)	0.020
Thyroid disease	0.96 (0.36–2.54)	0.927
Bronchiectasis	1.32 (0.70–2.52)	0.391
Chronic bronchitis	0.95 (0.55–1.66)	0.860
Previous history or current status of TB	1.24 (0.87–1.78)	0.229
Previous history of pneumonia	1.46 (0.94–2.26)	0.092
Asthma	0.97 (0.72–1.31)	0.843
Allergic rhinitis	1.36 (0.80–2.30)	0.251
Beck’s depression inventory score ≥16c	2.39 (1.02–5.59)	0.045

Notes: Model 1 was adjusted for age, sex, body mass index, education, smoking status, cough, sputum, dyspnea, and number of comorbidities. Model 2 was adjusted for each comorbidity with all of the abovementioned variables in Model 1 except for number of comorbidities.

a The numbers of missing/unknown data are as follows: cough (n=10), sputum (n=12), myocardial infarction (n=38), congestive heart failure (n=38), peripheral vascular disease (n=43), diabetes mellitus (n=8), hypertension (n=7), osteoporosis (n=31), gastroesophageal reflux disease (n=42), hyperlipidemia (n=46), thyroid disease (n=39), bronchiectasis (n=97), chronic bronchitis (n=106), previous history or current status of TB (n=29), previous history of pneumonia (n=51), asthma (n=43), and allergic rhinitis (n=39).

b Depression was not included in the number of comorbidities.

c Evaluated in 198 patients.

Abbreviations: COPD, chronic obstructive pulmonary disease; mMRC, modified Medical Research Council; OR, odds ratio; SGRQ-C, St George’s Respiratory Questionnaire for COPD; TB, tuberculosis.

Table 4 Multivariate logistic regression analysis of the factors associated with high SGRQ-C score (SGRQ-C score ≥25) in severe-to-very severe COPD patients

	Adjusted OR (95% CI)	p-value
Model 1
Age, years	1.01 (0.98–1.05)	0.490
Sex	0.49 (0.08–2.93)	0.434
Body mass index ≤21 kg/m^2	1.61 (0.87–2.99)	0.127
Smoking status
Never smoker	Reference	–
Ex-smoker	4.76 (1.54–14.77)	0.007
Current smoker	2.57 (0.77–8.62)	0.126
Education ≤ high school education	1.19 (0.47–3.01)	0.714
Cougha	1.49 (0.58–3.83)	0.407
Sputuma	2.87 (1.18–6.99)	0.021
Dyspnea (≥ mMRC II)	4.92 (2.67–9.06)	<0.001
Number of comorbiditiesb	1.00 (0.82–1.23)	0.978
Model 2
Comorbiditya
Myocardial infarction	0.64 (0.20–1.99)	0.437
Congestive heart failure	0.81 (0.23–2.83)	0.741
Peripheral vascular disease	3.00 (0.32–27.78)	0.334
Diabetes mellitus	0.83 (0.37–1.83)	0.639
Hypertension	0.70 (0.38–1.29)	0.250
Osteoporosis	NA	NA
Gastroesophageal reflux disease	1.65 (0.50–5.47)	0.411
Hyperlipidemia	0.98 (0.29–3.29)	0.975
Thyroid disease	0.47 (0.03–7.51)	0.591
Bronchiectasis	1.01 (0.36–2.81)	0.988
Chronic bronchitis	3.96 (0.46–34.42)	0.213
Previous history or current status of TB	1.39 (0.68–2.83)	0.363
Previous history of pneumonia	2.23 (0.84–5.91)	0.108
Asthma	0.97 (0.53–1.77)	0.910
Allergic rhinitis	0.79 (0.30–2.06)	0.625
Beck’s depression inventory score ≥16c	1.59 (0.42–6.00)	0.496

Notes: Model 1 was adjusted for age, sex, body mass index, education, smoking status, cough, sputum, dyspnea, and number of comorbidities. Model 2 was adjusted for each comorbidity with all of the abovementioned variables in Model 1 except for number of comorbidities.

a The numbers of missing/unknown data are as follows: cough (n=3), sputum (n=6), myocardial infarction (n=10), congestive heart failure (n=11), peripheral vascular disease (n=11), diabetes mellitus (n=2), hypertension (n=5), osteoporosis (n=10), gastroesophageal reflux disease (n=9), hyperlipidemia (n=8), thyroid disease (n=8), bronchiectasis (n=22), chronic bronchitis (n=26), previous history or current status of TB (n=14), previous history of pneumonia (n=16), asthma (n=18), and allergic rhinitis (n=14).

b Depression was not included in the number of comorbidities.

c Evaluated in 124 patients.

Abbreviations: COPD, chronic obstructive pulmonary disease; mMRC, modified Medical Research Council; OR, odds ratio; SGRQ-C, St George’s Respiratory Questionnaire for COPD; TB, tuberculosis.